ET20's are a budget, medium back, 3 lever, operator chair chair. They are finished with a black fabric upholstered back rest and seat pan.
Their features include :
Back Height - 410 mm
Back Width - 430 mm
Seat Depth - 460 mm
Seat Width - 480 mm
Seat Height - 420 mm to 530 mm
Summary - Chair clips together out of the box, no tools are required.
Recommendations - Very easy to do yourself, if you have the time.